/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.mpp.execution.operator.schema;

import com.google.common.util.concurrent.ListenableFuture;
import org.apache.iotdb.db.mpp.common.header.ColumnHeader;
import org.apache.iotdb.db.mpp.common.header.ColumnHeaderConstant;
import org.apache.iotdb.db.mpp.execution.operator.Operator;
import org.apache.iotdb.db.mpp.execution.operator.OperatorContext;
import org.apache.iotdb.db.mpp.execution.operator.process.ProcessOperator;
import org.apache.iotdb.tsfile.file.metadata.enums.TSDataType;
import org.apache.iotdb.tsfile.read.common.block.TsBlock;
import org.apache.iotdb.tsfile.utils.Binary;

import java.util.*;
import java.util.stream.Collectors;

import static com.google.common.util.concurrent.Futures.successfulAsList;
import static java.util.Objects.requireNonNull;

public class SchemaQueryOrderByHeatOperator implements ProcessOperator {

    private final OperatorContext operatorContext;
    private final List<Operator> operators;
    private final List<TsBlock> showTimeSeriesResult;
    private final List<TsBlock> lastQueryResult;

    private final List<TSDataType> outputDataTypes;
    private final int columnCount;

    private final boolean[] noMoreTsBlocks;
    private List<TsBlock> resultTsBlockList;
    private int currentIndex = 0;

    public SchemaQueryOrderByHeatOperator(OperatorContext operatorContext, List<Operator> operators) {
        this.operatorContext = requireNonNull(operatorContext, "operatorContext is null");
        this.operators = operators;
        this.showTimeSeriesResult = new ArrayList<>();
        this.lastQueryResult = new ArrayList<>();
        this.outputDataTypes =
                ColumnHeaderConstant.showTimeSeriesColumnHeaders.stream()
                        .map(ColumnHeader::getColumnType)
                        .collect(Collectors.toList());
        this.columnCount = outputDataTypes.size();

        noMoreTsBlocks = new boolean[operators.size()];
    }

    @Override
    public TsBlock next() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        if (resultTsBlockList != null) {
            currentIndex++;
            return resultTsBlockList.get(currentIndex - 1);
        }

        boolean allChildrenReady = true;
        Operator operator;
        for (int i = 0; i < operators.size(); i++) {
            if (!noMoreTsBlocks[i]) {
                operator = operators.get(i);
                if (operator.isFinished()) {
                    noMoreTsBlocks[i] = true;
                } else {
                    if (operator.hasNextWithTimer()) {
                        TsBlock tsBlock = operator.nextWithTimer();
                        if (null != tsBlock && !tsBlock.isEmpty()) {
                            if (isShowTimeSeriesBlock(tsBlock)) {
                                showTimeSeriesResult.add(tsBlock);
                            } else {
                                lastQueryResult.add(tsBlock);
                            }
                        }
                    }
                }
            }
            if (!noMoreTsBlocks[i]) {
                allChildrenReady = false;
            }
        }

        if (allChildrenReady) {
            generateResultTsBlockList();
            currentIndex++;
            return resultTsBlockList.get(currentIndex - 1);
        } else {
            return null;
        }
    }

    private void generateResultTsBlockList() {
        // Step 1: get last point result
        Map<String, Long> timeseriesToLastTimestamp = new HashMap<>();
        for (TsBlock tsBlock : lastQueryResult) {
            for (int i = 0; i < tsBlock.getPositionCount(); i++) {
                String timeseries = tsBlock.getColumn(0).getBinary(i).toString();
                long time = tsBlock.getTimeByIndex(i);
                timeseriesToLastTimestamp.put(timeseries, time);
            }
        }

        // Step 2: get last point timestamp to timeseries map
        Map<Long, List<Object[]>> lastTimestampToTsSchema = new HashMap<>();
        for (TsBlock tsBlock : showTimeSeriesResult) {
            TsBlock.TsBlockRowIterator tsBlockRowIterator = tsBlock.getTsBlockRowIterator();
            while (tsBlockRowIterator.hasNext()) {
                Object[] line = tsBlockRowIterator.next();
                String timeseries = line[0].toString();
                long time = timeseriesToLastTimestamp.getOrDefault(timeseries, 0L);
                if (!lastTimestampToTsSchema.containsKey(time)) {
                    lastTimestampToTsSchema.put(time, new ArrayList<>());
                }
                lastTimestampToTsSchema.get(time).add(line);
            }
        }

        // Step 3: sort by last point's timestamp
        List<Long> timestamps = new ArrayList<>(lastTimestampToTsSchema.keySet());
        timestamps.sort(Comparator.reverseOrder());

        // Step 4: generate result
        this.resultTsBlockList =
                SchemaTsBlockUtil.transferSchemaResultToTsBlockList(
                        timestamps.iterator(),
                        outputDataTypes,
                        (time, tsBlockBuilder) -> {
                            List<Object[]> rows = lastTimestampToTsSchema.get(time);
                            for (Object[] row : rows) {
                                tsBlockBuilder.getTimeColumnBuilder().writeLong(0L);
                                for (int i = 0; i < columnCount; i++) {
                                    Object value = row[i];
                                    if (null == value) {
                                        tsBlockBuilder.getColumnBuilder(i).appendNull();
                                    } else {
                                        tsBlockBuilder.getColumnBuilder(i).writeBinary(new Binary(value.toString()));
                                    }
                                }
                                tsBlockBuilder.declarePosition();
                            }
                        });
    }

    @Override
    public OperatorContext getOperatorContext() {
        return operatorContext;
    }

    @Override
    public ListenableFuture<?> isBlocked() {
        List<ListenableFuture<?>> listenableFutureList = new ArrayList<>(operators.size());
        for (int i = 0; i < operators.size(); i++) {
            if (noMoreTsBlocks[i]) {
                continue;
            }
            ListenableFuture<?> isBlocked = operators.get(i).isBlocked();
            if (!isBlocked.isDone()) {
                listenableFutureList.add(isBlocked);
            }
        }
        return listenableFutureList.isEmpty() ? NOT_BLOCKED : successfulAsList(listenableFutureList);
    }

    private boolean isShowTimeSeriesBlock(TsBlock tsBlock) {
        return tsBlock.getValueColumnCount() == columnCount;
    }

    @Override
    public boolean hasNext() {
        return resultTsBlockList == null || currentIndex < resultTsBlockList.size();
    }

    @Override
    public void close() throws Exception {
        for (Operator operator : operators) {
            operator.close();
        }
    }

    @Override
    public boolean isFinished() {
        return !hasNextWithTimer();
    }

    @Override
    public long calculateMaxPeekMemory() {
        long maxPeekMemory = 0;

        for (Operator child : operators) {
            maxPeekMemory += child.calculateMaxReturnSize();
        }

        for (Operator child : operators) {
            maxPeekMemory = Math.max(maxPeekMemory, child.calculateMaxPeekMemory());
        }

        return maxPeekMemory;
    }

    @Override
    public long calculateMaxReturnSize() {
        long maxReturnSize = 0;

        for (Operator child : operators) {
            maxReturnSize += child.calculateMaxReturnSize();
        }

        return maxReturnSize;
    }

    @Override
    public long calculateRetainedSizeAfterCallingNext() {
        long retainedSize = 0L;

        for (Operator child : operators) {
            retainedSize += child.calculateMaxReturnSize();
        }

        for (Operator child : operators) {
            retainedSize += child.calculateRetainedSizeAfterCallingNext();
        }
        return retainedSize;
    }
}
